equilibrium Flashcards
define the term dynamic equilibrium .
- the rate of the forward reaction is equal to the rate of the reverse reaction, + conc are constant.
(the conc of reactants and product do not change/ not equal.)
give an essential condition for an equilibrium mixture.
- equilibrium occurs in closed system (reactants and products cannot escape)
or macroscopic properties don’t change with time.
what happens at equilibrium ?
- the forward and reverse reactions still happening.
- the rate of forward and reverse reactions is the same
- the concentration of reactants and products remains constant .
state the Le Chatelier’s principle.
- if a system at equilibrium is disturbed, the equilibrium moves in the direction that tends to reduce the disturbance .
what effect does temperature have on the position of equilibrium ?
- increased temp = shifts in endothermic to reverse the change
- decreased temp = equilibrium moves exothermic direction to reverse the change.
in the equation: CH4 + H2O ⇌ CO + 3H2 = +210 kJ mol-1
what effect would increasing the temp have on position of equilibrium?
- equilibrium position shifts to the right
- as forward reaction is endothermic . yield of hydrogen increases .
what effect does pressure have on the position of equilibrium ?
- increased pressure = shifts direction that produces smaller number of molecules of gases to decrease pressure again
- decreased pressure = shifts to direction that produces larger number molecules of gas to increase pressure again
in the equation : CH4 + H2O ⇌ CO + 3H2
what effect would increasing pressure have on position of equilibrium ?
- equilibrium position shifts to the left.
- as the forward reaction is produced more moles of gas than the reverse reaction ( 4 moles of products, 2 moles of reactants) yield of hydrogen decreases .
suggest + explain why an industrial chemist may use a high pressure for this production of hydrogen from above reaction?
1) high pressure increases collision frequency , increasing the rate of reaction
2) this is a compromise pressure between an economically viable rate of reaction and slightly lower yield of hydrogen.
what effect does a catalyst have on the position of equilibrium?
- no effect = doesn’t change position of equilibrium.
- as it speeds up the forward and reverse reactions by the same amount .
what are the moderate conditions that may be used for industrial processes ?
- low pressures result in slow rate of reaction
- high pressures are expensive to generate , quite specialist equipment and may result in unwanted side reaction.
- low. temp result in slow rate of reaction
- high temp are expensive and involve burning lots of fuel - releases CO2 so not environmentally friendly
what’s meant by equilibrium constant ?
- the ration of concentrations when equilibrium is reached in a reversible reaction.
how to calculate Kc ?
products
————
reactants
define heterogeneous equilibrium .
- an equilibrium in which the reactants and products are in different states
define homogeneous equilibrium.
- an equilibrium in which all reactants are in same state .
